Furnace for heating



Dec. 5, 1939. J c WOODSON 2,182,218

FURNACE FOR HEATING Filed Aug. 16, 1938 2 Sheets-Sheet l INVENTOR JamesC. WoodSon Dec. 5, 1939. r J c. w ooDsbN 2,182,218

FURNACE FOR HEATING Filed Aug. 16, 1938 2 Sheets-Sheet 2 WW AW Av 30 IINVENTOR James C. Woodson Patented Dec. 5, 1939 UNITED STATES PATENTOFFICE FURNACE FOR HEATING Application August 16,

3 Claims.

This invention relates generally to the heating of materials in furnacesand has particular reference to a furnace for and method of heatingmaterials such as strip metal in coils.

The annealing of strip steel in coils has now become the acceptedpractice in the industry. Various methods and apparatus have beendevised for expediting this step in the processing of sheet steel, butthe operation remains a costly and time-consuming one at best. I havediscovered that heat supplied to strip in coils penetrates the interiorof the mass largely by conduction inwardly from the edges; i. e.,axially of the coil, instead of radially thereof through the layersformed by the successive turns of the coil. Following up this discovery,I have invented a novel furnace and method particularly adapted forheating strip in coils.

In a preferred practice of the invention, I

subject the sides of the coil to direct radiation and supply heat to theends of the coil by convection and conduction. The apparatus which Ihave invented for carrying out this method comprises a furnace having ahearth, side walls, and

a roof with heat exchange tubes mounted interiorly thereof, preferablyin spaced relation along the side walls. In order to increase theradiation surface, I form the tubes of hairpin shape and mount them sothey extend upwardly along the side walls and then downwardly thereof.Burners supply fuel to the tubes for combustion therein. Openings in thetubes adjacent the ends remote from those into which the bumers extendallow the combustion gases to be dis- 85 charged into the interior ofthe furnace after passing through the tube. An exhaust duct below thehearth and suitable connections thereto permit ,these gases to be drawnover the coil which is disposed on a support spaced above the hearth,

to supply heat to the edge of the strip by convection and conduction.

The following detailed description of the invention refers to theaccompanying drawings illustrating a preferred embodiment and practiceof the invention. In the drawings Figure 1 is a partial longitudinalsection through one form of furnace constructed in accordance with theinvention, for the practice of the method herein disclosed; and

Figure 2 is a transverse section through said furnace.

Referring now in detail to the drawings, a furnace I0 of the so-calledcover type comprises a base i I forming a hearth and a heating cover I2.65 The base is composed of refractory brick I3 laid 1938, Serial No.225,125

up on a bottom sheet I4 supported on structural frame members l5. Thebase is disposed on any suitable foundation or. working floor IS.

The cover I 2 comprises side walls I! and a roof l8 which are also builtup on refractory brick 5 within a housing formed by structural framemembers I9 and sheathing plates 20. The cover is removably disposable onthe base II, the lower edge of the cover being provided with a bearingplate 2| adapted to rest on the top flange of a 10 beam 22 extendingalong the sides of the base. A sealing channel 23 also extends aroundthe sides of the base and is adapted toreceive a sealing flange 24depending from the bottom edges of the cover. 15

Charge supports 25 are carried on the base and spaced slightlythereabove by pillars 26. The supports 25 may conveniently be in theform of heavy cast metal discs and preferably having a peripheralsealing channel 21. The pillars 26' permit the circulation of highcombustion gases under the charge support for heating the latter byconvection as will be explained further hereinafter. A plurality ofsupports 25 may be arranged on the base in one or more rows, dependingon the desired capacity of the apparatus. The supports 25 are adapted toreceive charges of material to be heated in the form of coils such asthat indicated at 28. The coils are disposed on the supports while theheating cover I2 is removed from the base H. Protective covers 29 aredisposed over the individual coils with their lower edges seated in thechannel 21. These covers protect the coil from atmospheric oxidation onremoval of the heating cover after the coils have been heated to thedesired temperature for annealing. The heating cover, of course, islowered over the coils and protective covers and deposited on the baseto effect such heating. Pipe connections 30 extend inwardly and upwardlythrough the base I! and the supports 25 for supplying a non-oxidizingatmosphere in the space within the covers 29.

Heat exchange tubes 3! are mounted in spaced relation along the sidewalls H for radiating heat 4,5 to the tubes 29 and thence to the coils28. The tubes 3| are preferably of hairpin shape as shown and haveelbows 32 at one end extending outwardly through the side walls ll. Asshown, the tubes are mounted substantially vertically. 50 Burners 33extend into the elbows 32 for supplying fuel thereto for combustion withair induced into the tubes. The burners are supplied from manifolds 34and each burner has a control valve 35 as well as a spark gap igniter36. A string thereon by the suspension 32a and a hook adapted to engagethe bend in the tube. The ends of the tubes 3| remote from those intowhich the burners 33 extend are open to permit the high combustion gasesto be discharged into the space within the heating cover I! aftertraversing both legs of the tubes.

An exhaust duct 31 extends longitudinally of the furnace beneath thefloor "5. Connecting pipes 38 extending through the base II anddepending therefrom cooperate with ports 39 branching from the duct 31.Annular sealing cups 40 extend around the ports 39 and receive the lowerends of the pipes'38. By means of these pipes and the duct 31, the hotcombustion gases discharged from the open ends of the tubes 3| blowaround the protective covers 39, under the charge supports 25, andthence downwardly through the pipes 38 to the duct 31 to a suitabledischarge stack.

As will be apparent from the foregoing description, the tubes 3| areheated to radiant temperature by the combustion of gases therein andsupply heat by direct radiation to the covers 29 which, whensufliciently heated, radiate heat to the sides of the coils 28. Thisheat soaks into the coil radially thereof by passing through the layersformed by the successive turns of the coil. The hot combustion gasesdischarged from the open ends of the tubes 3| and flowing under thesupports exhaust heat to the supports by convection and the lattertransmit-heat directly to the coilsby conduction. This heat soaksupwardly through the coil by conduction axially thereof from the loweredge of the coil toward the upper edge. The downward flow of thecombustion gases also has the effect of heating the refractory brickcomposing the hearth or base II to a temperature such that they radiateheat to the charge supports for conduction into th coils.

The invention thus provides a method and apparatus for heating coilsmore efiiciently than anything of the kind known previously with which Iam familar. The tubes 3|, being of hairpin shape, present a substantialradiating surface for delivering heat to the coils at the sides thereof.It will be understood, of course, that the tubes 3| also radiate heat tothe refractory lining of the side walls which, on being heatedsufliciently re-radiate such heat through the coils. By heating thecoils from the lower end thereof by convection and conduction,furthermore, the heating stage of the annealing cycle is expeditedconsiderably, reducing the time and fuel consumption heretofore involvedin this operation and increasing the production obtainable with a givenamount of equipment.

Although I have illustrated but a preferred embodiment and practice ofthe invention, it will be understood that changes therein may be madewithout departing from the spirit of the invention or the scope of theappended claims.

I claim:

1. A metallurgical furnace comprising a base covered with a refractorylayer, a charge support on said base, means mounting said support invertically spaced relation to said base, an outlet through said layerbelow said support, a cover disposable on said base, said cover havingsubstantially vertically disposed hairpin-shaped heat-exchange tubesmounted on the inner surface of the wall of the cover, each tube havinga burner in one end and an opening near the other, whereby hotcombustion gases traversing said tubes heat a charge on said support byradiation and flow under the support to said outlet thereby heating thesupport by convection.

2. In a furnace, a base, a charge support mounted on said base andspaced thereabove, a cover removably disposable over said base andsupport, hairpin-shaped heat-exchange tubes mounted on the inner surfaceof the walls of said cover, burners extending into said tubes, saidtubes having openings therein whereby the hot combustion gases travelingtherethrough are eventually discharged into the interior of said cover,and an outlet for said gases below said support and extending throughsaid base, whereby the outfiowing gases sweep across the lower surfaceof said support.

3. An annealing furnace comprising a base, a charge support, meansmounting said support in spaced relation to said base, an outlet throughsaid base below said support, a cover disposable on said base, aplurality of hairpin-shaped heatexchange tubes mounted on the innersurface of the wall of said cover, a burner in one end of each tube andan opening adjacent the other end whereby combustion gases aftertraversing said tubes are discharged into said furnace and flow acrossthe lower surface of said support and through said outlet.

JAMES C. WOODSON.

